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Introduction to Chemistry
Introduction to Chemistry is the first unit in the Year 11 Preliminary Course. Introduction Matter Matter is anything that has mass and occupies space or volume. It can be both invisible and visible. Energy Energy is anything that enables matter to change or move. It exists in many interchangable forms, namely heat, light and sound (among others). The Law of Conservation of Energy "Energy can neither be created nor destroyed but only changed from one form to another" The law of conservation of energy applies to all reactions except for nuclear reactions, in which some energy is transferred into matter and vice versa. The Atomic Theory The atomic theory is composed of 3 parts, that being; #All matter is composed of tiny particles called atoms that are so small they cannot be seen with the most powerful microscopes available #All atoms possess kinetic energy and are thus in a constant state of motion #Atoms exert attractive forces on each other Physical and Chemical Properties of Matter *Physical properties are those in which can be determined without changing the chemical composition of the substance (eg. colour, odour) *Chemical properties are those in which relate to the ability of a substance to form new substances Elements *Elements are the building blocks of matter *An element is simply another name for a type of atom or substance that is composed of only one type of atom *A full list of all atoms in existance can be found in the Periodic Table of the Elements Elements can be split into three major categories: Metals Metals are elements that have a metallic shine or lustre and generally have high melting and boiling points, and are good conductors of heat and electricity. Non-Metals A non-metal is an element that has a relatively low boiling and melting point and does not conduct electricity or heat. Usually, non-metals have such low boiling points that they exist as gases at room temperature and pressure. They are found in the top-right hand corner of the periodic table. Metalloids Metalloids have properties that lie in between metals and non-metals. They are partial conductors of heat and electricity and have some at gas, some at liquid and some at solid form at room temperature and pressure. Compounds *Compounds are pure substances that are composed of two or more different elements joined by chemical bonds *It is possible to decompose compounds into their individual parts (eg. H2O into H2 and O) by electrolysis or by heating them The Periodic Table of the Elements *All of the known elements are placed into the table according to the number of protons present in their atoms *There is important information contained within the table: Atomic Number The atomic number tells you how many protons there are present in that element. If the element is neutral, it also therefore tells you the amount of electrons present. Symbols Some of the symbols in the periodic table are based off the element's Latin names, eg. sodium in Latin is natrium, hence the symbol 'Na'. Other symbols are simply based off the English name for them, eg. Aluminium = Al. Atomic Weight The atomic mass unit of an atom was created by chemists in order to measure minute sub-atomic particles, like protons and neutrons. The mass of one proton is roughly equal to 1 u, the mass of one neutron is roughly equal to 1 u, and the mass of one electron is roughly equal to 5.5x10^-4 u. Thus, the mass of one proton is roughly 1800 times the mass of one electron. Because the mass of one proton and one neutron is roughly equal to 1 u (and the mass of one electron is so infinitely tiny in comparison) it can be said that the total mass of one atom is equal to the sum of protons and neutrons within that atom. This number is called the atomic mass number. (A) We are able to derive a formula: Number of Nuclear Particles = Number of Protons + Number of Neutrons Mass Number (A) = Atomic Number (Z) + Number of Neutrons thus Number of Neutrons = A - Z Atomic Notation Atomic notation is commonly used in order to derive the mass number and the atomic number of an atom.